Thermal elastic rotary impeller ink jet printing mechanism

ABSTRACT

An ink jet printer utilizing a rotary impeller mechanism to eject ink drops is described. The nozzle chamber includes a number of radial paddle wheel vanes; and a number of fixed paddles. Upon rotation of the paddle wheel, ink within the paddle chambers is pressurized, causing ink to be ejected from the ink ejection port. The ink ejection port is located above a pivot point of the paddle wheel and includes a wall which is located substantially on the circumference of the paddle wheel. The rotation of the paddle wheel is controlled by a thermal actuator which comprises an internal electrically resistive element and an external jacket around the resistive element, the jacket having a high coefficient of thermal expansion and being constructed from polytetrafluoroethylene. The thermal actuator undergoes circumferential expansion relative to the paddle wheel.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are hereby incorporated by cross- reference. For the purposes of location and identification, U.S. patent applications identified by their U.S. patent application Ser. Nos. are listed alongside the Australian applications from which the U.S. patent applications claim the right of priority.

CROSS-REFERENCED U.S. PAT. NO./PATIENT AUSTRALIAN APPLICATION (CLAIMING RIGHT PROVISIONAL PATENT OF PRIORITY FROM AUSTRALIAN APPLICATION NO. PROVISIONAL APPLICATION) DOCKET NO. PO7991 09/113,060 ART01 PO8505 09/113,070 ART02 PO7988 09/113,073 ART03 PO9395 09/112,748 ART04 PO8017 09/112,747 ART06 PO8014 09/112,776 ART07 PO8025 09/112,750 ART08 PO8032 09/112,746 ART09 PO7999 09/112,743 ART10 PO7998 09/112,742 ART11 PO8031 09/112,741 ART12 PO8030 09/112,740 ART13 PO7997 09/112,739 ART15 PO7979 09/113,053 ART16 PO8015 09/112,738 ART17 PO7978 09/113,067 ART18 PO7982 09/113,063 ART19 PO7989 09/113,069 ART20 PO8019 09/112,744 ART21 PO7980 09/113,058 ART22 PO8018 09/112,777 ART24 PO7938 09/113,224 ART25 PO8016 09/112,804 ART26 PO8024 09/112,805 ART27 PO7940 09/113,072 ART28 PO7939 09/112,785 ART29 PO8501 09/112,797 ART30 PO8500 09/112,796 ART31 PO7987 09/113,071 ART32 PO8022 09/112,824 ART33 PO8497 09/113,090 ART34 PO8020 09/112,823 ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO8000 09/113,051 ART43 PO7977 09/112,782 ART44 PO7934 09/113,056 ART45 PO7990 09/113,059 ART46 PO8499 09/113,091 ART47 PO8502 09/112,753 ART48 PO7981 09/113,055 ART50 PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO8026 09/112,752 ART53 PO8027 09/112,759 ART54 PO8028 09/112,757 ART56 PO9394 09/112,758 ART57 PO9396 09/113,107 ART58 PO9397 09/112,829 ART59 PO9398 09/112,792 ART60 PO9399 6,106,147 ART61 PO9400 09/112,790 ART62 PO9401 09/112,789 ART63 PO9402 09/112,788 ART64 PO9403 09/112,795 ART65 PO9405 09/112,749 ART66 PP0959 09/112,784 ART68 PP1397 09/112,783 ART69 PP2370 09/112,781 DOT01 PP2371 09/113,052 DOT02 PO8003 09/112,834 Fluid01 PO8005 09/113,103 Fluid02 PO9404 09/113,101 Fluid03 PO8066 09/112,751 IJ01 PO8072 09/112,787 IJ02 PO8040 09/112,802 IJ03 PO8071 09/112,803 IJ04 PO8047 09/113,097 IJ05 PO8035 09/113,099 IJ06 PO8044 09/113,084 IJ07 PO8063 09/113,066 IJ08 PO8057 09/112,778 IJ09 PO8056 09/112,779 IJ10 PO8069 09/113,077 IJ11 PO8049 09/113,061 IJ12 PO8036 09/112,818 IJ13 PO8048 09/112,816 IJ14 PO8070 09/112,772 IJI5 PO8067 09/112,819 IJ16 PO8001 09/112,815 IJ17 PO8038 09/113,096 IJ18 PO8033 09/113,068 IJ19 PO8002 09/113,095 IJ20 PO8068 09/112,808 IJ21 PO8062 09/112,809 IJ22 PO8034 09/112,780 IJ23 PO8039 09/113,083 IJ24 PO8041 09/113,121 IJ25 PO8004 09/113,122 IJ26 PO8037 09/112,793 IJ27 PO8043 09/112,794 IJ28 PO8042 09/113,128 IJ29 PO8064 09/113,127 IJ30 PO9389 09/112,756 IJ31 PO9391 09/112,755 IJ32 PP0888 09/112,754 IJ33 PP0891 09/112,811 IJ34 PP0890 09/112,812 IJ35 PP0873 09/112,813 IJ36 PP0993 09/112,814 IJ37 PP0890 09/112,764 IJ38 PP1398 09/112,765 IJ39 PP2592 09/112,767 IJ40 PP2593 09/112,768 IJ41 PP3991 09/112,807 IJ42 PP3987 09/112,806 IJ43 PP3985 09/112,820 IJ44 PP3983 09/112,821 IJ45 PO7935 09/112,822 IJM01 PO7936 09/112,825 IJM02 PO7937 09/112,826 IJM03 PO8061 09/112,827 IJM04 PO8054 09/112,828 IJM05 PO8065 6,071,750 IJM06 PO8055 09/113,108 IJM07 PO8053 09/113,109 IJM08 PO8078 09/113,123 IJM09 PO7933 09/113,114 IJM10 PO7950 09/113,115 IJM11 PO7949 09/113,129 IJM12 PO8060 09/113,124 IJM13 PO8059 09/113,125 IJM14 PO8073 09/113,126 IJM15 PO8076 09/113,119 IJM16 PO8075 09/113,120 IJM17 PO8079 09/113,221 IJM18 PO8050 09/113,116 IJM19 PO8052 09/113,118 IJM20 PO7948 09/113,117 IJM21 PO7951 09/113,113 IJM22 PO8074 09/113,130 IJM23 PO7941 09/113,110 IJM24 PO8077 09/113,112 IJM25 PO8058 09/113,087 IJM26 PO8051 09/113,074 IJM27 PO8045 6,111,754 IJM28 PO7952 09/113,088 IJM29 PO8046 09/112,771 IJM30 PO9390 09/112,769 IJM31 PO9392 09/112,770 IJM32 PP0889 09/112,798 IJM35 PP0887 09/112,801 IJM36 PP0882 09/112,800 IJM37 PP0874 09/112,799 IJM38 PP1396 09/113,098 IJM39 PP3989 09/112,833 IJM40 PP2591 09/112,832 IJM41 PP3990 09/112,831 IJM42 PP3986 09/112,830 IJM43 PP3984 09/112,836 IJM44 PP3982 09/112,835 IJM45 PP0895 09/113,102 IR01 PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP0887 09/113,104 IR05 PP0885 09/112,810 IR06 PP0884 09/112,766 IR10 PP0886 09/113,085 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP0877 09/112,760 IR16 PP0878 09/112,773 IR17 PP0879 09/112,774 IR18 PP0883 09/112,775 IR19 PP0880 09/112,745 IR20 PP0881 09/113,092 IR21 PO8006 6,087,638 MEMS02 PO8007 09/113,093 MEMS03 PO8008 09/113,062 MEMS04 PO8010 6,041,600 MEMS05 PO8011 09/113,082 MEMS06 PO7947 6,067,797 MEMS07 PO7944 09/113,080 MEMS09 PO7946 6,044,646 MEMS10 PO9393 09/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP0894 09/113,075 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to ink jet printing and in particular discloses a thermal elastic rotary impeller ink jet printer.

The present invention further relates to the field of drop on demand ink jet printing.

BACKGROUND OF THE INVENTION

Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.

In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.

Many different techniques of ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207 to 220 (1988).

Ink Jet printers themselves come in many different types. The utilization of a continuous stream of ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al) Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.

Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques that rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.

As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction and operation, durability and consumables.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an alternative form of inkjet printing utilizing nozzles which include a rotary impeller mechanism to eject ink drops.

In accordance with a first aspect of the present invention an ink ejection nozzle arrangement is presented comprising an ink chamber having an ink ejection port, a pivotally mounted paddle wheel with a first plurality of radial paddle wheel vanes and a second plurality of fixed paddle chambers each of which has a corresponding one of the pivotally mounted paddle wheel vanes defining a surface of the paddle chamber such that upon rotation of the paddle wheel, ink within the paddle chambers is pressurized resulting in the ejection of ink through the ejection port. Further, the paddle chambers can include a side wall having a radial component relative to the pivotally mounted paddle wheel. Preferably, the ink ejection port is located above the pivot point of the paddle wheel. The radial components of the paddle chamber's side walls are located substantially on the circumference of the pivotally mounted paddle wheel. Advantageously, the rotation of the paddle wheel is controlled by a thermal actuator. The thermal actuator comprises an internal electrically resistive element and an external jacket around the resistive element, made of a material having a high coefficient of thermal expansion relative to the embedded resistive element. Further, the resistive element can be of a substantially serpentine form, and preferably, the outer jacket comprises substantially polytetrafluoroethylene. The thermal actuator can undergo circumferential expansion relative to the pivotally mounted paddle wheel.

In accordance with a second aspect of the present invention, a method is provided to eject ink from an ink jet nozzle interconnected to the ink chamber. The method comprises construction of a series of paddle chambers within the ink chamber, each of which has at least one moveable wall connected to a central pivoting portion activated by an activation means. After substantially filling the ink chamber with ink, utilisation of the activation means connected to the moveable walls to reduce the volume in the paddle chambers results in an increased ink pressure within the chambers and consequential ejection of ink from the inkjet nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is an exploded perspective view illustrating the construction of a single ink jet nozzle arrangement in accordance with a preferred embodiment of the present invention;

FIG. 2 is a plan view taken from above of relevant portions of an ink jet nozzle arrangement in accordance with the preferred embodiment;

FIG. 3 is a cross-sectional view through a single nozzle arrangement, illustrating a drop being ejected out of the nozzle aperture;

FIG. 4 provides a legend of the materials indicated in FIG. 5 to 17; and

FIG. 5 to FIG. 17 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet nozzle arrangement.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, a thermal actuator is utilized to activate a set of “vanes” so as to compress a volume of ink and thereby force ink out of an ink nozzle.

The preferred embodiment fundamentally comprises a series of vane chambers 2 which are normally filled with ink. The vane chambers 2 include side walls which define static vanes 3 each having a first radial wall 5 and a second circumferential wall 6. A set of “impeller vanes” 7 is also provided which each have a radially aligned surface and are attached to rings 9, 10 with the inner ring 9 being pivotally mounted around a pivot unit 12. The outer ring 10 is also rotatable about the pivot point 12 and is interconnected with thermal actuators 13, 22. The thermal actuators 13, 22 are of a circumferential form and undergo expansion and contraction thereby rotating the impeller vanes 7 towards the radial wall 5 of the static vanes 3. As a consequence the vane chamber 2 undergoes a rapid reduction in volume thereby resulting in a substantial increase in pressure resulting in the expulsion of ink from the chamber 2.

The static vane 3 is attached to a nozzle plate 15. The nozzle plate 15 includes a nozzle rim 16 defining an aperture 14 into the vane chambers 2. The aperture 14 defined by rim 16 allows for the injection of ink from the vane chambers 2 onto the relevant print media.

FIG. 2 shows a plan view taken from above of relevant portions of an ink jet nozzle arrangement 1, constructed in accordance with the preferred embodiment. The outer ring 10 is interconnected at points 20, 21 to thermal actuators 13, 22. The thermal actuators 13, 22 include inner resistive elements 24, 25 which are constructed from copper or the like. Copper has a low coefficient of thermal expansion and is therefore constructed in a serpentine manner, so as to allow for greater expansion in the radial direction 28. The inner resistive elements 24, 25 are each encased in an outer jacket 26 of a material having a high coefficient of thermal expansion. Suitable material includes polytetrafluoroethylene (PTFE) which has a high coefficient of thermal expansion (770×10⁻⁶). The thermal actuators 13, 22 is anchored at the points 27 to a lower layer of the wafer. The anchor points 27 also form an electrical connection with a relevant drive line of the lower layer. The resistive elements 24, 25 are also electronically connected at 20, 21 to the outer ring 10. Upon activation of the resistive element 24, 25, the outer jacket 26 undergoes rapid expansion which includes the expansion of the serpentine resistive elements 24, 25. The rapid expansion and subsequent contraction on de-energizing the resistive elements 24, 25 results in a rotational force in the direction 28 being induced in the ring 10. The rotation of the ring 10 causes a corresponding rotation in the relevant impeller vanes 7 (FIG. 1). Hence, by the activation of the thermal actuators 13, 22, ink can be ejected out of the nozzle aperture 14 (FIG. 1).

Turning now to FIG. 3, there is illustrated a cross-sectional view through a single nozzle arrangement. The illustration of FIG. 3 shows a drop 31 being ejected out of the nozzle aperture 14 as a result of displacement of the impeller vanes 7 (FIG. 1). The nozzle arrangement 1 is constructed on a silicon wafer 33. Electronic drive circuitry 34 is first constructed for control and driving of the thermal actuators 13, 22. A silicon dioxide layer 35 is provided for defining the nozzle chamber which includes channel walls separating ink of one color from an adjacent ink reservoirs (not shown). The nozzle plate 15, is also interconnected to the wafer 33 via nozzle plate posts, 37 so as to provide for stable separation from the wafer 33. The static vanes 3 are constructed from silicon nitrate as is the nozzle plate 15. The static vanes 3 and nozzle plate 15 can be constructed utilizing a dual damascene process utilizing a sacrificial layer as discussed further hereinafter.

One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads including a plane of the nozzle arrangement 1 can proceed utilizing the following steps:

1. Using a double sided polished wafer 33, complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process 34. Relevant features of the wafer at this step are shown in FIG. 5. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle arrangement 1. FIG. 4 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.

2. Deposit 1 micron of low stress nitride 35. This acts as a barrier to prevent ink diffusion through the silicon dioxide of the chip surface.

3. Deposit 2 microns of sacrificial material 50.

4. Etch the sacrificial layer using Mask 1. This mask defines the axis pivot and the anchor points 12 of the actuators. This step is shown in FIG. 6.

5. Deposit 1 micron of PTFE 51.

6. Etch the PTFE down to top level metal using Mask 2. This mask defines the heater contact vias. This step is shown in FIG. 7.

7. Deposit and pattern resist using Mask 3. This mask defines the heater, the vane support wheel, and the axis pivot.

8. Deposit 0.5 microns of gold 52 (or other heater material with a low Young s modulus) and strip the resist. Steps 7 and 8 form a lift-off process. This step is shown in FIG. 8.

9. Deposit 1 micron of PTFE 53.

10. Etch both layers of PTFE down to the sacrificial material using Mask 4. This mask defines the actuators and the bond pads. This step is shown in FIG. 9.

11. Wafer probe. All electrical connections are complete at this point, and the chips are not yet separated.

12. Deposit 10 microns of sacrificial material 55.

13. Etch the sacrificial material down to heater material or nitride using Mask 5. This mask defines the nozzle plate support posts and the moving vanes, and the walls surrounding each ink color. This step is shown in FIG. 10.

14. Deposit a conformal layer of a mechanical material and planarize to the level of the sacrificial layer. This material may be PECVD glass, titanium nitride, or any other material which is chemically inert, has reasonable strength, and has suitable deposition and adhesion characteristics. This step is shown in FIG. 11.

15. Deposit 0.5 microns of sacrificial material 56.

16. Etch the sacrificial material to a depth of approximately 1 micron above the heater material using Mask 6. This mask defines the fixed vanes 3 and the nozzle plate support posts, and the walls surrounding each ink color. As the depth of the etch is not critical, it may be a simple timed etch.

17. Deposit 3 microns of PECVD glass 58. This step is shown in FIG. 12.

18. Etch to a depth of 1 micron using Mask 7. This mask defines the nozzle rim 16. This step is shown in FIG. 13.

19. Etch down to the sacrificial layer using Mask 8. This mask defines the nozzle 14 and the sacrificial etch access holes 17. This step is shown in FIG. 14.

20. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask 9. This mask defines the ink inlets 60 which are etched through the wafer. The wafer is also diced by this etch. This step is shown in FIG. 15.

21. Back-etch the CMOS oxide layers and subsequently deposited nitride layers through to the sacrificial layer using the back-etched silicon as a mask.

22. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in FIG. 16.

23. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer.

24. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.

25. Hydrophobize the front surface of the printheads.

26. Fill the completed printheads with ink 61 and test them. A filled nozzle is shown in FIG. 17.

It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiment without departing from the spirit or scope of the invention as broadly described. The present embodiment is, therefore, to be considered in all respects to be illustrative and not restrictive.

The presently disclosed ink jet printing technology is potentially suited to a wide range of printing systems including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers, high speed pagewidth printers, notebook computers with in-built pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic ‘minilabs’, video printers, PHOTO CD (PHOTO CD is a registered trademark of the Eastman Kodak Company) printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per printhead, but is a major impediment to the fabrication of pagewidth printheads with 19,200 nozzles.

Ideally, the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new ink jet technologies have been created. The target features include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systems described below with differing levels of difficulty. Forty-five different ink jet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the table under the heading Cross References to Related Applications.

The ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems.

For ease of manufacture using standard process equipment, the printhead is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the printhead is 100 mm long, with a width which depends upon the ink jet type. The smallest printhead designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The printheads each contain 19,200 nozzles plus data and control circuitry.

Ink is supplied to the back of the printhead by injection molded plastic ink channels. The molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The printhead is connected to the camera circuitry by tape automated bonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of ink jet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of ink jet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain ink jet types have been investigated in detail. These are designated IJ01 to IJ45 above which matches the docket numbers in the table under the heading Cross References to Related Applications.

Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jet printheads with characteristics superior to any currently available ink jet technology.

Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ45 series are also listed in the examples column. In some cases, print technology may be listed more than once in a table, where it shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrix are set out in the following tables.

ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description Advantages Disadvantages Examples Thermal bubble An electrothermal heater heats Large force generated High power Canon Bubblejet 1979 Endo et the ink to above boiling point, Simple construction Ink carrier limited to water al GB patent 2,007,162 transferring significant heat to No moving parts Low efficiency Xerox heater-in-pit 1990 the aqueous ink. A bubble Fast operation High temperatures required Hawkins et al U.S. Pat. No. nucleates and quickly forms, Small chip area required for High mechanical stress 4,899,181 expelling the ink. The actuator Unusual materials required Hewlett-Packard TIJ 1982 efficiency of the process is low, Large drive transistors Vaught et al U.S. Pat. No. with typically less than 0.05% of Cavitation causes actuator 4,490,728 the electrical energy being failure transformed into kinetic energy Kogation reduces bubble forma- of the drop. tion Large print heads are difficult to fabricate Piezoelectric A piezoelectric crystal such as Low power consumption Very large area required for Kyser et al U.S. Pat. No. lead lanthanum zirconate (PZT) Many ink types can be used actuator 3,946,398 is electrically activated, and Fast operation Difficult to integrate with Zoltan U.S. Pat. No. 3,683,212 either expands, shears, or bends High efficiency electronics 1993 Stemme U.S. Pat. No. to apply pressure to the ink, High voltage drive transistors 3,747,120 ejecting drops. required Epson Stylus Full pagewidth print heads Tektronix impractical due to actuator size IJ04 Requires electrical poling in high field strengths during manufacture Electrostrictive An electric field is used to Low power consumption Low maximum strain (approx. Seiko Epson, Usui et all JP activate electrostriction in Many in types can be used 0.01%) 253401/96 relaxor materials such as lead Low thermal expansion Large are required for actuator IJ04 lanthanum zirconate titanate Electric field strength required due to low strain (PLZT) or lead magnesium (approx. 3.5 V/μm) can be Response speed is marginal niobate (PMN). generated without difficulty (˜10 μs) Does not require electrical High voltage drive transistors poling required Full pagewidth print heads impractical due to actuator size Ferroelectric An electric field is used to Low power consumption Difficult to integrate with IJ04 induce a phase transition Many ink types can be used electronics between the antiferroelectric Fast operation (<1 μs) Unusual materials such as (AFE) and ferroelectric (FE) Relatively high longitudinal PLZSnT are required phase. Perovskite materials strain Actuators require a large area such as tin modified lead High efficiency lanthanum zirconate titanate Electric field strength of (PLZSnT) exhibit large strains around 3 V/μm can be readily of up to 1% associated with the provided AFE to FE phase transition. Electrostatic Conductive plates are separated Low power consumption Difficult to operate electrostatic IJ02, IJ04 plates by a compressible or fluid Many ink types can be used devices in an aqueous environ- dielectric (usually air). Upon Fast operation ment application of a voltage, the The electrostatic actuator will plates attract each other and normally need to be separated displace ink, causing drop from the ink ejection. The conductive plates Very large area required to may be in a comb or honeycomb achieve high forces structure, or stacked to increase High voltage drive transistors the surface area and therefore may be required the force. Full pagewidth print heads are not competitive due to actuator actuator size Electrostatic A strong electric field is applied Low current consumption High voltage required 1989 Saito et al, U.S. Pat. No. pull on ink to the ink, whereupon electro- Low temperature May be damaged by sparks due 4,799,068 static attraction accelerates the to air breakdown 1989 Miura et al, U.S. Pat. No. ink towards the print medium. Required field strength increases 4,810,954 as the drop size decreases Tone-jet High voltage drive transistors required Electrostatic field attracts dust Permanent An electromagnet directly Low power consumption Complex fabrication IJ07, IJ10 magnet electro- attracts a permanent magnet, Many ink types can be used Permanent magnetic material magnetic displacing ink and causing Fast operation such as Neodymium Iron Boron drop ejection. Rare earth High efficiency (NdFeB) required. magnets with a field strength Easy extension from single High local currents required around 1 Telsa can be used. nozzles to pagewidth print Copper metalization should be Examples are: Samarium Cobalt heads used for long electromigration (SaCo) and magnetic materials lifetime and low resistivity in the neodymium iron boron Pigmented inks are usually family (NdFeB, NdDyFeBNb, infeasible NdDyFeB, etc) Operating temperature limited to the Curie temperature (around 540 K.) Soft magnetic A solenoid induced a magnetic Low power consumption Complex fabrication core electro- field in a soft magnetic core or Many ink types can be used Materials not usually present in IJ01, IJ05, IJ08, IJ10, IJ12, IJ14, magnetic yoke fabricated from a ferrous Fast operation a CMOS fab such as NiFe, IJ15, IJ17 material such as electroplated High efficiency CoNiFe, or CoFe are required iron alloys such as CoNiFe [1], Easy extension from single High local currents required CoFe, or NiFe alloys. Typically, nozzles to pagewidth print Copper metalization should be the soft magnetic material is in heads used for long electromigration two parts, which are normally lifetime and low resistivity held apart by a spring. When the Electroplating is required solenoid is actuated, the two High saturation flux density is parts attract, displacing the required (2.0-2.1 T is ink. achievable with CoNiFe [1]) Lorenz force The Lorenz force acting on a Low power consumption Force acts as a twisting motion IJ06, IJ11, IJ13, IJ16 current carrying wire in a Many ink types can be used Typically, only a quarter of the magnetic field is utilized. This Fast operation solenoid length provides force in allows the magnetic field to be High efficiency a useful direction supplied externally to the print Easy extension from single High local currents required head, for example with rare nozzles to pagewidth print Copper metalization should be earth permanent magnets. Only heads used for long electromigration the current carrying wire need lifetime and low resistivity be fabricated on the print-head, Pigmented inks are usually simplifying materials require- infeasible ments. Magneto- The actuator uses the giant Many ink types can be used Force acts as a twisting motion Fischenbeck, U.S. Pat. No. striction magnetostrictive effect of Fast operation Unusual materials such as 4,032,929 materials such as Terfenol-D Easy extension from single Terfenol-D are required IJ25 (an alloy of terbium, nozzles to pagewidth print heads High local currents required dysprosium and iron developed High force is available Copper metalization should be at the Naval Ordnance used for long electromigration Laboratory, hence Ter-Fe-NOL). lifetime and low resistivity For best efficiency, the Pre-stressing may be required actuator should be pre-stressed to approx. 8 MPa. Surface tension Ink under positive pressure is Low power consumption Requires supplementary force to Silverbrook, EP 0771 658 A2 reduction held in a nozzle by surface Simple construction effect drop separation and related patent applications tension. The surface tension No unusual materials required in Requires special ink surfactants of the ink is reduced below the fabrication Speed may be limited by sur- bubble threshold, causing the High efficiency factant properties ink to egress from the nozzle. Easy extension from single nozzles to pagewidth print heads Viscosity The ink viscosity is locally Simple construction Requires supplementary force to Silverbrook, EP 0771 658 A2 reduction reduced to select which drops No unusual materials required in effect drop separation and related patent applications are to be ejected. A viscosity fabrication Requires special ink viscosity reduction can be achieved Easy extension from single properties electrothermally with most inks, nozzles to pagewidth print heads High speed is difficult to achieve but special inks can be engineer- Requires oscillating ink pressure ed for a 100:1 viscosity reduc- A high temperature difference tion. (typically 80 degrees) is required Acoustic An acoustic wave is generated Can operate without a nozzle Complex drive circuitry 1993 Hadimioglu et al, EUP and focussed upon the drop plate Complex fabrication 550,192 ejection region. Low efficiency 1993 Elrod et al, EUP 572,220 Poor control of drop position Poor control of drop volume Thermoelastic An actuator which relies upon Low power consumption Efficient aqueous operation IJ03, IJ09, IJ17, IJ18, IJ19, IJ20, bend actuator differential thermal expansion Many ink types can be used requires a thermal insulator on IJ21, IJ22, IJ23, IJ24, IJ27, IJ28, upon Joule heating is used. Simple planar fabrication the hot side IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, Small chip area required for Corrosion prevention can be IJ35, IJ36, IJ37, IJ38, IJ39, IJ40, each actuator difficult IJ41 Fast operation Pigmented inks may be infeas- High efficiency ible, as pigment particles may CMOS compatible voltages and jam the bend actuator currents Standard MEMS processes can be used Easy extension from single nozzles to pagewidth print heads High CTE A material with a very high High force can be generated Requires special material (e.g. IJ09, IJ17, IJ18, IJ20, IJ21, IJ22, thermoelastic coefficient of thermal expansion Three methods of PTFE deposi- PTFE) IJ23, IJ24, IJ27, IJ28, IJ29, IJ30, actuator (CTE) such as polytetrafluoro- tion are under development: Requires a PTFE deposition pro- IJ31, IJ42, IJ43, IJ44 ethylene (PTFE) is used. As chemical vapor deposition cess, which is not yet standard high CTE materials are usually (CVD), spin coating, and in ULSI fabs non-conductive, a heater fabri- evaporation PTFE deposition cannot be cated from a conductive material PTFE is a candidate for low followed with high temperature is incorporated. A 50 μm long dielectric constant insulation (above 350° C.) processing PTFE bend actuator with poly- in ULSI Pigmented inks may be infeas- silicon heater and 15 mW power Very low power consumption ible, as pigment particles may input can provide 180 μN force Many ink types can be used jam the bend actuator and 10 μm deflection. Actuator Simple planar fabrication motions include: Small chip area required for Bend each actuator Push Fast operation Buckle High efficiency Rotate CMOS compatible voltages and currents Easy extension from single nozzles to pagewidth print heads Conductive A polymer with a high co- High force can be generated Requires special materials IJ24 polymer efficient of thermal expansion Very low power consumption development (High CTE con- thermoelastic (such as PTFE) is doped with Many ink types can be used ductive polymer) actuator conducting substances to Simple planar fabrication Requires a PTFE deposition increase its conductivity to Small chip area required for process, which is not yet about 3 order of magnitude each actuator standard in ULSI fabs below that of copper. The Fast operation PTFE deposition cannot be conducting polymer expands High efficiency followed with high temperature when resistively heated. CMOS compatible voltages and (above 350° C.) processing Examples of conducting dopants currents Evaporation and CVD deposi- include: Easy extension from single tion techniques cannot be used Carbon nanotubes nozzles to pagewidth print heads Pigmented inks may be infeas- Metal fibers ible, as pigment particles may Conductive polymers such as jam the bend actuator doped polythiophene Carbon granules Shape memory A shape memory alloy such as High force is available Fatigue limits maximum number IJ26 alloy TiNi (also known as Nitinol - (stresses of hundreds of MPa) of cycles Nickel Titanium alloy develop- Large strain is available Low strain (1%) is required to ed at the Naval Ordnance (more than 3%) extend fatigue resistance Laboratory) is thermally High corrosion resistance Cycle rate limited by head switched between its weak Simple construction removal martensitic state and its high Easy extension from single Requires unusual materials stiffness austenic state. The nozzles to pagewidth print heads (TiNi) shape of the actuator in its Low voltage operation The latent heat of transformation martensitic state is deformed must be provided relative to the austenic shape. High current operation The shape change causes Requires pre-stressing to distort ejection of a drop. the martensitic state Linear Mag- Linear magnetic actuators Linear Magnetic actuators can Requires unusual semiconductor IJ12 netic Actuator include the Linear Induction be constructed with high thrust, materials such as soft magnetic Actuator (LIA), Linear long travel, and high efficiency alloys (e.g. CoNiFe) Permanent Magnet Synchronous using planar semiconductor Some varieties also require Actuator (LPMSA), Linear fabrication techniques permanent magnetic materials Reluctance Synchronous Long actuator travel is available such as Neodymium iron boron Actuator (LRSA), Linear Medium force is available (NdFeB) Switched Reluctance Actuator Low voltage operation Requires complex multi-phase (LSRA), and the Linear Stepper drive circuitry Actuator (LSA). High current operation

BASIC OPERATION MODE Description Advantages Disadvantages Examples Actuator This is the simplest mode of Simple operation Drop repetition rate is usually Thermal ink jet directly pushes operation: the actuator directly No external fields required limited to around 10 kHz. How- Piezoelectric ink jet ink supplies sufficient kinetic energy Satellite drops can be avoided if ever, this is not fundamental to IJ01, IJ02, IJ03, IJ04, IJ05, IJ06, to expel the drop. The drop must drop velocity is less than 4 m/s the method, but is related to IJ07, IJ09, IJ11, IJ12, IJ14, IJ16, have a sufficient velocity to Can be efficient, depending the refill method normally used IJ20, IJ22, IJ23, IJ24, IJ25, IJ26, overcome the surface tension. upon the actuator used All of the drop kinetic energy IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, must be provided by the actuator IJ33, IJ34, IJ35, IJ36, IJ37, IJ38, Satellite drops usually form if IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 drop velocity is greater than 4.5 m/s Proximity The drops to be printed are Very simple print head fabrica- Requires close proximity Silverbrook, EP 0771 658 A2 selected by some manner (e.g. tion can be used between the print head and the and related patent applications thermally induced surface The drop selection means does print media or transfer roller tension reduction of pressurized not need to provide the energy May require two print heads ink). Selected drops are required to separate the drop printing alternate rows of the separated from the ink in the from the nozzle image nozzle by contact with the Monolithic color print heads are print medium or a transfer difficult roller. Electrostatic The drops to be printed are Very simple print head fabrica- Requires very high electrostatic Silverbrook, EP 0771 658 A2 pull on ink selected by some manner (e.g. tion can be used field and related patent applications thermally induced surface The drop selection means does Electrostatic field for small Tone-Jet tension reduction of pressurized not need to provide the energy nozzle sizes is above air break- ink). Selected drops are required to separate the drop down separated from the ink in the from the nozzle Electrostatic field may attract nozzle by a strong electric dust field. Magnetic pull The drops to be printed are Very simple print head fabrica- Requires magnetic ink Silverbrook, EP 0771 658 A2 on ink selected by some manner (e.g. tion can be used Ink colors other than black are and related patent applications thermally induced surface The drop selection means does difficult tension reduction of pressurized not need to provide the energy Requires very high magnetic ink). Selected drops are required to separate the drop fields separated from the ink in the from the nozzle nozzle by a strong magnetic field acting on the magnetic ink. Shutter The actuator moves a shutter to High speed (>50 kHz) operation Moving parts are required IJ13, IJ17, IJ21 block ink flow to the nozzle. can be achieved due to reduced Requires ink pressure modulator The ink pressure is pulsed at a refill time Friction and wear must be multiple of the drop ejection Drop timing can be very considered frequency. accurate Stiction is possible The actuator energy can be very low Shuttered The actuator moves a shutter to Actuators with small travel can Moving parts are required IJ08, IJ15, IJ18, IJ19 grill block ink flow through a grill to be used Requires ink pressure modulator the nozzle. The shutter move- Actuators with small force can Friction and wear must be con- ment need only be equal to the be used sidered width of the grill holes. High speed (>50 kHz) operation Stiction is possible can be achieved Pulsed mag- A pulsed magnetic field attracts Extremely low energy operation Requires an external pulsed IJ10 netic pull on an ‘ink pusher’ at the drop is possible magnetic field ink pusher ejection frequency. An actuator No heat dissipation problems Requires special materials for controls a catch, which prevents both the actuator and the ink the ink pusher from moving pusher when a drop is not to be ejected. Complex construction

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description Advantages Disadvantages Examples None The actuator directly Simplicity of Drop ejection Most inkjets, fires the ink drop, and construction energy must be including there is no external Simplicity of supplied by piezoelectric and field or other operation individual nozzle thermal bubble. mechanism required. Small physical actuator IJ01, IJ02, IJ03, size IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24, IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The ink pressure Oscillating ink Requires external Silverbrook, EP ink pressure oscillates, providing pressure can provide ink pressure 0771 658 A2 and (including much of the drop a refill pulse, oscillator related patent acoustic ejection energy. The allowing higher Ink pressure applications stimul- actuator selects which operating speed phase and amplitude IJ08, IJ13, IJ15, ation) drops are to be fired The actuators must be carefully IJ17, IJ15, IJ19, by selectively may operate with controlled IJ21 blocking or enabling much lower energy Acoustic nozzles. The ink Acoustic lenses reflections in the ink pressure oscillation can be used to focus chamber must be may be achieved by the sound on the designed for vibrating the print nozzles head, or preferably by an actuator in the ink supply. Media The print head is Low power Precision Silverbrook, EP proximity placed in close High accuracy assembly required 0771 658 A2 and proximity to the print Simple print head Paper fibers may related patent medium. Selected construction cause problems applications drops protrude from Cannot print on the print head further rough substrates than unselected drops, and contact the print medium. The drop soaks into the medium fast enough to cause drop separation. Transfer Drops are printed to a High accuracy Bulky Silverbrook, EP roller transfer roller instead Wide range of Expensive 0771 658 A2 and of straight to the print print substrates can Complex related patent medium. A transfer be used construction applications roller can also be used Ink can be dried Tektronix hot for proximity drop on the transfer roller melt piezoelectric separation. inkjet Any of the IJ series Electro- An electric field is Low power Field strength Silverbrook, EP static used to accelerate Simple print head required for 0771 658 A2 and selected drops towards construction separation of small related patent the print medium. drops is near or applications above air Tone-Jet breakdown Direct A magnetic field is Low power Requires Silverbrook, EP magnetic used to accelerate Simple print head magnetic ink 0771 658 A2 and field selected drops of construction Requires strong related patent magnetic ink towards magnetic field applications the print medium. Cross The print head is Does not require Requires external IJ06, IJ16 magnetic placed in a constant magnetic materials magnet field magnetic field. The to be integrated in Current densities Lorenz force in a the print head may be high, current carrying wire manufacturing resulting in is used to move the process electromigration actuator. problems Pulsed A pulsed magnetic Very low power Complex print IJ10 magnetic field is used to operation is possible head construction field cyclically attract a Small print head Magnetic paddle, which pushes size materials required in on the ink. A small print head actuator moves a catch, which selectively prevents the paddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description Advantages Disadvantages Examples None No actuator Operational Many actuator Thermal Bubble mechanical simplicity mechanisms have Inkjet amplification is used. insufficient travel, IJ01, IJ02, IJ06, The actuator directly or insufficient force, IJ07, IJ16, IJ25, drives the drop to efficiently drive IJ26 ejection process. the drop ejection process Differential An actuator material Provides greater High stresses are Piezoelectric expansion expands more on one travel in a reduced involved IJ03, IJ09, IJ17, bend side than on the other. print head area Care must be IJ18, IJ19, IJ20, actuator The expansion may be taken that the IJ21, IJ22, IJ23, thermal, piezoelectric, materials do not IJ24, IJ27, IJ29, magnetostrictive, or delaminate IJ30, IJ31, IJ32, other mechanism. The Residual bend IJ33, IJ34, IJ35, bend actuator converts resulting from high IJ36, IJ37, IJ38, a high force low travel temperature or high IJ39, IJ42, IJ43, actuator mechanism to stress during IJ44 high travel, lower formation force mechanism. Transient A trilayer bend Very good High stresses are IJ40, IJ41 bend actuator where the two temperature stability involved actuator outside layers are High speed, as a Care must be identical. This cancels new drop can be taken that the bend due to ambient fired before heat materials do not temperature and dissipates delaminate residual stress. The Cancels residual actuator only responds stress of formation to transient heating of one side or the other. Reverse The actuator loads a Better coupling Fabrication IJ05, IJ11 spring spring. When the to the ink complexity actuator is turned off, High stress in the the spring releases. spring This can reverse the force/distance curve of the actuator to make it compatible with the force/time requirements of the drop ejection. Actuator A series of thin Increased travel Increased Some stack actuators are stacked. Reduced drive fabrication piezoelectric inkjets This can be voltage complexity IJ04 appropriate where Increased actuators require high possibility of short electric field strength, circuits due to such as electrostatic pinholes and piezoelectric actuators. Multiple Multiple smaller Increases the Actuator forces IJ12, IJ13, IJ18, actuators actuators are used force available from may not add IJ20, IJ22, IJ28, simultaneously to an actuator linearly, reducing IJ42, IJ43 move the ink. Each Multiple efficiency actuator need provide actuators can be only a portion of the positioned to control force required. ink flow accurately Linear A linear spring is used Matches low Requires print IJ15 Spring to transform a motion travel actuator with head area for the with small travel and higher travel spring high force into a requirements longer travel, lower Non-contact force motion. method of motion transformation Coiled A bend actuator is Increases travel Generally IJ17, IJ21, IJ34, actuator coiled to provide Reduces chip restricted to planar IJ35 greater travel in a area implementations reduced chip area. Planar due to extreme implementations are fabrication difficulty relatively easy to in other orientations. fabricate. Flexure A bend actuator has a Simple means of Care must be IJ10, IJ19, IJ33 bend small region near the increasing travel of taken not to exceed actuator fixture point, which a bend actuator the elastic limit in flexes much more the flexure area readily than the Stress remainder of the distribution is very actuator. The actuator uneven flexing is effectively Difficult to converted from an accurately model even coiling to an with finite element angular bend, resulting analysis in greater travel of the actuator tip. Catch The actuator controls a Very low Complex IJ10 small catch. The catch actuator energy construction either enables or Very small Requires external disables movement of actuator size force an ink pusher that is Unsuitable for controlled in a bulk pigmented inks manner. Gears Gears can be used to Low force, low Moving parts are IJ13 increase travel at the travel actuators can required expense of duration. be used Several actuator Circular gears, rack Can be fabricated cycles are required and pinion, ratchets, using standard More complex and other gearing surface MEMS drive electronics methods can be used. processes Complex construction Friction, friction, and wear are possible Buckle plate A buckle plate can be Very fast Must stay within S. Hirata et al, used to change a slow movement elastic limits of the “An Ink-jet Head actuator into a fast achievable materials for long Using Diaphragm motion. It can also device life Microactuator”, convert a high force, High stresses Proc. IEEE MEMS, low travel actuator involved Feb. 1996, pp 418- into a high travel, Generally high 423. medium force motion. power requirement IJ18, IJ27 Tapered A tapered magnetic Linearizes the Complex IJ14 magnetic pole can increase magnetic construction pole travel at the expense force/distance curve of force. Lever A lever and fulcrum is Matches low High stress IJ32, IJ36, IJ37 used to transform a travel actuator with around the fulcrum motion with small higher travel travel and high force requirements into a motion with Fulcrum area has longer travel and no linear movement, lower force. The lever and can be used for can also reverse the a fluid seal direction of travel. Rotary The actuator is High mechanical Complex IJ28 impeller connected to a rotary advantage construction impeller. A small The ratio of force Unsuitable for angular deflection of to travel of the pigmented inks the actuator results in actuator can be a rotation of the matched to the impeller vanes, which nozzle requirements push the ink against by varying the stationary vanes and number of impeller out of the nozzle. vanes Acoustic A refractive or No moving parts Large area 1993 Hadimioglu lens diffractive (e.g. zone required et al, EUP 550, 192 plate) acoustic lens is Only relevant for 1993 Elrod et al, used to concentrate acoustic inkjets EUP 572,220 sound waves. Sharp A sharp point is used Simple Difficult to Tone-jet conductive to concentrate an construction fabricate using point electrostatic field. standard VLSI processes for a surface ejecting ink- jet Only relevant for electrostatic inkjets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume The volume of the Simple High energy is Hewlett-Packard expansion actuator changes, construction in the typically required to Thermal Inkjet pushing the ink in all case of thermal ink achieve volume Canon Bubblejet directions. jet expansion. This leads to thermal stress, cavitation, and kogation in thermal ink jet implementations Linear, The actuator moves in Efficient High fabrication IJ01, IJ02, IJ04, normal to a direction normal to coupling to ink complexity may be IJ07, IJ11, IJ14 chip surface the print head surface. drops ejected required to achieve The nozzle is typically normal to the perpendicular in the line of surface motion movement. Parallel to The actuator moves Suitable for Fabrication IJ12, IJ13, IJ15, chip surface parallel to the print planar fabrication complexity IJ33,, IJ34, IJ35, head surface. Drop Friction IJ36 ejection may still be Stiction normal to the surface. Membrane An actuator with a The effective Fabrication 1982 Howkins push high force but small area of the actuator complexity USP 4,459,601 area is used to push a becomes the Actuator size stiff membrane that is membrane area Difficulty of in contact with the ink. integration in a VLSI process Rotary The actuator causes Rotary levers Device IJ05, IJ08, IJ13, the rotation of some may be used to complexity IJ28 element, such a grill or increase travel May have impeller Small chip area friction at a pivot requirements point Bend The actuator bends A very small Requires the 1970 Kyser et al when energized. This change in actuator to be made USP 3,946,398 may be due to dimensions can be from at least two 1973 Stemme differential thermal converted to a large distinct layers, or to USP 3,747,120 expansion, motion. have a thermal IJ03, IJ09, IJ10, piezoelectric difference across the IJ19, IJ23, IJ24, expansion, actuator IJ25, IJ29, IJ30, magnetostriction, or IJ31, IJ33, IJ34, other form of relative IJ35 dimensional change. Swivel The actuator swivels Allows operation Inefficient IJ06 around a central pivot. where the net linear coupling to the ink This motion is suitable force on the paddle motion where there are is zero opposite forces Small chip area applied to opposite requirements sides of the paddle, e.g. Lorenz force. Straighten The actuator is Can be used with Requires careful IJ26, IJ32 normally bent, and shape memory balance of stresses straightens when alloys where the to ensure that the energized. austenic phase is quiescent bend is planar accurate Double The actuator bends in One actuator can Difficult to make IJ36, IJ37, IJ38 bend one direction when be used to power the drops ejected by one element is two nozzles. both bend directions energized, and bends Reduced chip identical. the other way when size. A small another element is Not sensitive to efficiency loss energized. ambient temperature compared to equivalent single bend actuators. Shear Energizing the Can increase the Not readily 1985 Fishbeck actuator causes a shear effective travel of applicable to other USP 4,584,590 motion in the actuator piezoelectric actuator material. actuators mechanisms Radial con- The actuator squeezes Relatively easy High force 1970 Zoltan USP striction an irk reservoir, to fabricate single required 3,683,212 forcing ink from a nozzles from glass Inefficient constricted nozzle. tubing as Difficult to macroscopic integrate with VLSI structures processes Coil/uncoil A coiled actuator Easy to fabricate Difficult to IJ17, IJ21, IJ34, uncoils or coils more as a planar VLSI fabricate for non- IJ35 tightly. The motion of process planar devices the free end of the Small area Poor out-of-plane actuator ejects the ink. required, therefore stiffness low cost Bow The actuator bows (or Can increase the Maximum travel IJ16, IJ18, IJ27 buckles) in the middle speed of travel is constrained when energized. Mechanically High force rigid required Push-Pull Two actuators control The structure is Not readily IJ18 a shutter. One actuator pinned at both ends, suitable for inkjets pulls the shutter, and so has a high out-of- which directly push the other pushes it. plane rigidity the ink Curl A set of actuators curl Good fluid flow Design IJ20, IJ42 inwards inwards to reduce the to the region behind complexity volume of ink that the actuator they enclose. increases efficiency Curl A set of actuators curl Relatively simple Relatively large IJ43 outwards outwards, pressurizing construction chip area ink in a chamber surrounding the actuators, and expelling ink from a nozzle in the chamber. Iris Multiple vanes enclose High efficiency High fabrication IJ22 a volume of ink. These Small chip area complexity simultaneously rotate, Not suitable for reducing the volume pigmented inks between the vanes. Acoustic The actuator vibrates The actuator can Large area 1993 Hadimioglu vibration at a high frequency. be physically distant required for et al, EUP 550,192 from the ink efficient operation 1993 Elrod et al, at useful frequencies EUP 572,220 Acoustic coupling and crosstalk Complex drive circuitry Poor control of drop volume and position None In various ink jet No moving parts Various other Silverbrook, EP designs the actuator tradeoffs are 0771 658 A2 and does not move. required to related patent eliminate moving applications parts Tone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages Examples Surface This is the normal way Fabrication Low speed Thermal inkjet tension that inkjets are simplicity Surface tension Piezoelectric ink refilled. After the Operational force relatively jet actuator is energized, simplicity small compared to IJ01-IJ07, IJ10- it typically returns actuator force IJ14, IJ16, IJ20, rapidly to its normal Long refill time IJ22-IJ45 position. This rapid usually dominates return sucks in air the total repetition through the nozzle rate opening. The ink surface tension at the nozzle then exerts a small force restoring the meniscus to a minimum area. This force refills the nozzle. Shuttered Ink to the nozzle High speed Requires IJ08, IJ13, IJ15, oscillating chamber is provided at Low actuator common ink IJ17, IJ18, IJ19, ink pressure a pressure that energy, as the pressure oscillator IJ21 oscillates at twice the actuator need only May not be drop ejection open or close the suitable for frequency. When a shutter, instead of pigmented inks drop is to be ejected, ejecting the ink drop the shutter is opened for 3 half cycles: drop ejection, actuator return, and refill. The shutter is then closed to prevent the nozzle chamber emptying during the next negative pressure cycle. Refill After the main High speed, as Requires two IJ09 actuator actuator has ejected a the nozzle is independent drop a second (refill) actively refilled actuators per nozzle actuator is energized. The refill actuator pushes ink into the nozzle chamber. The refill actuator returns slowly, to prevent its return from emptying the chamber again. Positive ink The ink is held a slight High refill rate, Surface spill Silverbrook, EP pressure positive pressure. therefore a high must be prevented 0771 658 A2 and After the ink drop is drop repetition rate Highly related patent ejected, the nozzle is possible hydrophobic print applications chamber fills quickly head surfaces are Alternative for:, as surface tension and required IJ01-IJ07, IJ10-IJ14, ink pressure both IJ16, IJ20, IJ22-IJ45 operate to refill the nozzle.

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description Advantages Disadvantages Examples Long inlet The ink inlet channel Design simplicity Restricts refill Thermal inkjet channel to the nozzle chamber Operational rate Piezoelectric ink is made long and simplicity May result in a jet relatively narrow, Reduces relatively large chip IJ42, IJ43 relying on viscous crosstalk area drag to reduce inlet Only partially back-flow. effective Positive ink The ink is under a Drop selection Requires a Silverbrook, EP pressure positive pressure, so and separation method (such as a 0771 658 A2 and that in the quiescent forces can be nozzle rim or related patent state some of the ink reduced effective applications drop already protrudes Fast refill time hydrophobizing, or Possible from the nozzle. both) to prevent operation of the This reduces the flooding of the following: IJ01- pressure in the nozzle ejection surface of IJ07, IJ09-IJ12, chamber which is the print head. IJ14, IJ16, IJ20, required to eject a IJ22,, IJ23-IJ34, certain volume of ink. IJ36-IJ41, IJ44 The reduction in chamber pressure results in a reduction in ink pushed out through the inlet. Baffle One or more baffles The refill rate is Design HP Thermal Ink are placed in the inlet not as restricted as complexity Jet irk flow. When the the long inlet May increase Tektronix actuator is energized, method. fabrication piezoelectric inkjet the rapid ink Reduces complexity (e.g. movement creates crosstalk Tektronix hot melt eddies which restrict Piezoelectric print the flow through the heads). inlet. The slower refill process is unrestricted, and does not result in eddies. Flexible flap In this method recently Significantly Not applicable to Canon restricts disclosed by Canon, reduces back-flow most inkjet inlet the expanding actuator for edge-shooter configurations (bubble) pushes on a thermal inkjet Increased flexible flap that devices fabrication restricts the inlet. complexity Inelastic deformation of polymer flap results in creep over extended use Inlet filter A filter is located Additional Restricts refill IJ04, IJ12, IJ24, between the ink inlet advantage of ink rate IJ27, IJ29, IJ30 and the nozzle filtration May result in chamber. The filter Ink filter may be complex has a multitude of fabricated with no construction small holes or slots, additional process restricting ink flow. steps The filter also removes particles which may block the nozzle. Small inlet The ink inlet channel Design simplicity Restricts refill IJ02, IJ37, IJ44 compared to the nozzle chamber rate to nozzle has a substantially May result in a smaller cross section relatively large chip than that of the nozzle, area resulting in easier ink Only partially egress out of the effective nozzle than out of the inlet. Inlet shutter A secondary actuator Increases speed Requires separate IJ09 controls the position of of the ink-jet print refill actuator and a shutter, closing off head operation drive circuit the ink inlet when the main actuator is energized. The inlet is The method avoids the Back-flow Requires careful IJ01, IJ03, IJ05, located problem of inlet back- problem is design to minimize IJ06, IJ07, IJ10, behind the flow by arranging the eliminated the negative IJ11, IJ14, IJ16, ink-pushing ink-pushing surface of pressure behind the IJ22, IJ23, IJ25, surface the actuator between paddle IJ28, IJ31, IJ32, the inlet and the IJ33, IJ34, IJ35, nozzle. IJ36, IJ39, IJ40, IJ41 Part of the The actuator and a Significant Small increase in IJ07, IJ20, IJ26, actuator wall of the ink reductions in back- fabrication IJ38 moves to chamber are arranged flow can be complexity shut off the so that the motion of achieved inlet the actuator closes off Compact designs the inlet. possible Nozzle In some configurations Ink back-flow None related to Silverbrook, EP actuator of inkjet, there is no problem is ink back-flow on 0771 658 A2 and does not expansion or eliminated actuation related patent result in ink movement of an applications back-flow actuator which may Valve-jet cause ink back-flow Tone-jet through the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages Examples Normal All of the nozzles are No added May not be Most inkjet nozzle firing fired periodically, complexity on the sufficient to systems before the ink has a print head displace dried ink IJ01, IJ02, IJ03, chance to dry. When IJ04, IJ05, IJ06, not in use the nozzles IJ07, IJ09, IJ10, are sealed (capped) IJ11, IJ12, IJ14, against air. IJ16, IJ20, IJ22, The nozzle firing is IJ23, IJ24, IJ25, usually performed IJ26, IJ27, IJ28, during a special IJ29, IJ30, IJ31, clearing cycle, after IJ32, IJ33, IJ34, first moving the print IJ36, IJ37, IJ38, head to a cleaning IJ39, IJ40,, IJ41, station. IJ42, IJ43, IJ44,, IJ45 Extra In systems which heat Can be highly Requires higher Silverbrook, EP power to the ink, but do not boil effective if the drive voltage for 0771 658 A2 and ink heater it under normal heater is adjacent to clearing related patent situations, nozzle the nozzle May require applications clearing can be larger drive achieved by over- transistors powering the heater and boiling ink at the nozzle. Rapid The actuator is fired in Does not require Effectiveness May be used success-ion rapid succession. In extra drive circuits depends with: IJ01, IJ02, of actuator some configurations, on the print head substantially upon IJ03, IJ04, IJ05, pulses this may cause heat Can be readily the configuration of IJ06, IJ07, IJ09, build-up at the nozzle controlled and the inkjet nozzle IJ10, IJ11, IJ14, which boils the ink, initiated by digital IJ16, IJ20, IJ22, clearing the nozzle. In logic IJ23, IJ24, IJ25, other situations, it may IJ27, IJ28, IJ29, cause sufficient IJ30, IJ31, IJ32, vibrations to dislodge IJ33, IJ34, IJ36, clogged nozzles. IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is A simple Not suitable May be used power to not normally driven to solution where where there is a with: IJ03, IJ09, ink pushing the limit of its motion, applicable hard limit to IJ16, IJ20, IJ23, actuator nozzle clearing may be actuator movement IJ24, IJ25, IJ27, assisted by providing IJ29, IJ30, IJ31, an enhanced drive IJ32, IJ39, IJ40, signal to the actuator. IJ41, IJ42, IJ43, IJ44, IJ45 Acoustic An ultrasonic wave is A high nozzle High IJ08, IJ13, IJ15, resonance applied to the ink clearing capability implementation cost IJ17, IJ18, IJ19, chamber. This wave is can be achieved if system does not IJ21 of an appropriate May be already include an amplitude and implemented at very acoustic actuator frequency to cause low cost in systems sufficient force at the which already nozzle to clear include acoustic blockages. This is actuators easiest to achieve if the ultrasonic wave is at a resonant frequency of the ink cavity. Nozzle A microfabricated Can clear Accurate Silverbrook, EP clearing plate is pushed against severely clogged mechanical 0771 658 A2 and plate the nozzles. The plate nozzles alignment is related patent has a post for every required applications nozzle. A post moves Moving parts are through each nozzle, required displacing dried ink. There is risk of damage to the nozzles Accurate fabrication is required Ink The pressure of the ink May be effective Requires May be used pressure is temporarily where other pressure pump or with all IJ series ink pulse increased so that ink methods cannot be other pressure jets streams from all of the used actuator nozzles. This may be Expensive used in conjunction Wasteful of ink with actuator energizing. Print head A flexible ‘blade’ is Effective for Difficult to use if Many inkjet wiper wiped across the print planar print head print head surface is systems head surface. The surfaces non-planar or very blade is usually Low cost fragile fabricated from a Requires flexible polymer, e.g. mechanical parts rubber or synthetic Blade can wear elastomer. out in high volume print systems Separate A separate heater is Can be effective Fabrication Can be used with ink boiling provided at the nozzle where other nozzle complexity many IJ series ink heater although the normal clearing methods jets drop e-ection cannot be used mechanism does not Can be require it. The heaters implemented at no do not require additional cost in individual drive some inkjet circuits, as many configurations nozzles can be cleared simultaneously, and no imaging is required.

NOZZLE PLATE CONSTRUCTION Description Advantages Disadvantages Examples Electro- A nozzle plate is Fabrication High Hewlett Packard formed separately fabricated simplicity temperatures and Thermal Ink jet nickel from electroformed pressures are nickel, and bonded to required to bond the print head chip. nozzle plate Minimum thickness constraints Differential thermal expansion Laser Individual nozzle No masks Each hole must Canon Bubblejet ablated or holes are ablated by an required be individually 1988 Sercel et drilled intense UV laser in a Can be quite fast formed al., SPIE, Vol. 998 polymer nozzle plate, which is Some control Special Excimer Beam typically a polymer over nozzle profile equipment required Applications, pp. such as polyimide or is possible Slow where there 76-83 polysulphone Equipment are many thousands 1993 Watanabe required is relatively of nozzles per print et al., U.S. Pat. No. low cost head 5,208,604 May produce thin burrs at exit holes Silicon A separate nozzle High accuracy is Two part K. Bean, IEEE micro- plate is attainable construction Transactions on machined micromachined from High cost Electron Devices, single crystal silicon, Requires Vol. ED-25, No. 10, and bonded to the precision alignment 1978, pp 1185-1195 print head wafer. Nozzles may be Xerox 1990 clogged by adhesive Hawkins et al., U.S. Pat. No. 4,899,181 Glass Fine glass capillaries No expensive Very small 1970 Zoltan U.S. Pat. No. capillaries are drawn from glass equipment required nozzle sizes are 3,683,212 tubing. This method Simple to make difficult to form has been used for single nozzles Not suited for making individual mass production nozzles, but is difficult to use for bulk manufacturing of print heads with thousands of nozzles. Monolithic, The nozzle plate is High accuracy Requires Silverbrook, EP surface deposited as a layer (<1 μm) sacrificial layer 0771 658 A2 and micro- using standard VLSI Monolithic under the nozzle related patent machined deposition techniques. Low cost plate to form the applications using VLSI Nozzles are etched in Existing nozzle chamber IJ01, IJ02, IJ04, litho- the nozzle plate using processes can be Surface may be IJ11, IJ12, IJ17, graphic VLSI lithography and used fragile to the touch IJ18, IJ20, IJ22, processcs etching. IJ24, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is a High accuracy Requires long IJ03, IJ05, IJ06, etched buried etch stop in the (<1 μm) etch times IJ07, IJ08, IJ09, through wafer. Nozzle Monolithic Requires a IJ10, IJ13, IJ14, substrate chambers are etched in Low cost support wafer IJ15, IJ16, IJ19, the front of the wafer, No differential IJ21, IJ23, IJ25, and the wafer is expansion IJ26 thinned from the back side. Nozzles are then etched in the etch stop layer. No nozzle Various methods have No nozzles to Difficult to Ricoh 1995 plate been tried to eliminate become clogged control drop Sekiya et al U.S. Pat. No. the nozzles entirely, to position accurately 5,412,413 prevent nozzle Crosstalk 1993 Hadimioglu clogging. These problems et al EUP 550,192 include thermal bubble 1993 Elrod et al mechanisms and EUP 572,220 acoustic lens mechanisms Trough Each drop ejector has Reduced Drop firing IJ35 a trough through manufacturing direction is sensitive which a paddle moves. complexity to wicking. There is no nozzle Monolithic plate. Nozzle slit The elimination of No nozzles to Difficult to 1989 Saito et al instead of nozzle holes and become clogged control drop U.S. Pat. No. 4,799,068 individual replacement by a slit position accurately nozzles encompassing many Crosstalk actuator positions problems reduces nozzle clogging, but increases crosstalk due to ink surface waves

DROP EJECTION DIRECTION Description Advantages Disadvantages Examples Edge Ink flow is along the Simple Nozzles limited Canon Bubblejet (‘edge surface of the chip, construction to edge 1979 Endo et al GB shooter’) and ink drops are No silicon High resolution patent 2,007,162 ejected from the chip etching required is difficult Xerox heater-in- edge. Good heat Fast color pit 1990 Hawkins et sinking via substrate printing requires al U.S. Pat. No. 4,899,181 Mechanically one print head per Tone-jet strong color Ease of chip handing Surface Ink flow is along the No bulk silicon Maximum ink Hewlett-Packard (‘roof surface of the chip, etching required flow is severely TIJ 1982 Vaught et shooter’) and ink drops are Silicon can make restricted al U.S. Pat. No. 4,490,728 ejected from the chip an effective heat IJ02, IJ11, IJ12, surface, normal to the sink IJ20, IJ22 plane of the chip. Mechanical strength Through Ink flow is through the High ink flow Requires bulk Silverbrook, EP chip, chip, and ink drops are Suitable for silicon etching 0771 658 A2 and forward ejected from the front pagewidth print related patent (‘up surface of the chip. heads applications shooter’) High nozzle IJ04, IJ17, IJ18, packing density IJ24, IJ27-IJ45 therefore low manufacturing cost Through Ink flow is through the High ink flow Requires wafer IJ01, IJ03, IJ05, chip, chip, and ink drops are Suitable for thinning IJ06, IJ07, IJ08, reverse ejected from the rear pagewidth print Requires special IJ09, IJ10, IJ13, (‘down surface of the chip. heads handling during IJ14, IJ15, IJ16, shooter’) High nozzle manufacture IJ19, IJ21, IJ23, packing density IJ25, IJ26 therefore low manufacturing cost Through Ink flow is through the Suitable for Pagewidth print Epson Stylus actuator actuator, which is not piezoelectric print heads require Tektronix hot fabricated as part of heads several thousand melt piezoelectric the same substrate as connections to drive ink jets the drive transistors. circuits Cannot be manufactured in standard CMOS fabs Complex assembly required

INK TYPE Description Advantages Disadvantages Examples Aqueous, Water based ink which Environmentally Slow drying Most existing ink dye typically contains: friendly Corrosive jets water, dye, surfactant, No odor Bleeds on paper All IJ series ink humectant, and May jets biocide. strikethrough Silverbrook, EP Modern ink dyes have Cockles paper 0771 658 A2 and high water-fastness, related patent light fastness applications Aqueous, Water based ink which Environmentally Slow drying IJ02, IJ04, IJ21, pigment typically contains: friendly Corrosive IJ26, IJ27, IJ30 water, pigment, No odor Pigment may Silverbrook, EP surfactant, humectant, Reduced bleed clog nozzles 0771 658 A2 and and biocide. Reduced wicking Pigment may related patent Pigments have an Reduced clog actuator applications advantage in reduced strikethrough mechanisms Piezoelectric ink- bleed, wicking and Cockles paper jets strikethrough. Thermal ink jets (with signiflcant restrictions) Methyl MEK is a highly Very fast drying Odorous All IJ series ink Ethyl volatile solvent used Prints on various Flammable jets Ketone for industrial printing substrates such as (MEK) on difficult surfaces metals and plastics such as aluminum cans. Alcohol Alcohol based inks Fast drying Slight odor All IJ series ink (ethanol, 2- can be used where the Operates at sub- Flammable jets butanol, printer must operate at freezing and others) temperatures below temperatures the freezing point of Reduced paper water. An example of cockle this is in-camera Low cost consumer photographic printing. Phase The ink is solid at No drying time- High viscosity Tektronix hot change room temperature, and ink instantly freezes Printed ink melt piezoelectric (hot melt) is melted in the print on the print medium typically has a ink jets head before jetting. Almost any print ‘waxy’ feel 1989 Nowak Hot melt inks are medium can be used Printed pages U.S. Pat. No. 4,820,346 usually wax based, No paper cockle may ‘block’ All IJ series ink with a melting point occurs Ink temperature jets around 80° C. After No wicking may be above the jetting the ink freezes occurs curie point of almost instantly upon No bleed occurs permanent magnets contacting the print No strikethrough Ink heaters medium or a transfer occurs consume power roller. Long warm-up time Oil Oil based inks are High solubility High viscosity: All IJ series ink extensively used in medium for some this is a significant jets offset printing. They dyes limitation for use in have advantages in Does not cockle ink jets, which improved paper usually require a characteristics on Does not wick low viscosity. Some paper (especially no through paper short chain and wicking or cockle). multi-branched oils Oil soluble dies and have a sufficiently pigments are required. low viscosity. Slow drying Micro- A microemulsion is a Stops ink bleed Viscosity higher All IJ series ink emulsion stable, self forming High dye than water jets emulsion of oil, water, solubility Cost is slightly and surfactant. The Water, oil, and higher than water characteristic drop size amphiphilic soluble based ink is less than 100 nm, dies can be used High surfactant and is determined by Can stabilize concentration the preferred curvature pigment required (around of the surfactant. suspensions 5%) 

I claim:
 1. An ink ejection nozzle arrangement having an ink ejection port, the nozzle arrangement comprising: a plurality of side walls which define a plurality of vane chambers; a pivotally mounted paddle wheel; and a plurality of radial paddle wheel vanes attached to the paddle wheel, the paddle wheel vanes being positioned with respect to the side walls and being configured so that rotary movement of the paddle wheel results in each wheel vane rotating with respect to the side walls so that ink within said paddle chambers can be pressurized, said pressurization causing ink to be ejected from the ink ejection port.
 2. An ink ejection nozzle arrangement as claimed in claim 1 wherein the side walls include walls positioned radially with respect to the paddle wheel.
 3. An ink ejection nozzle arrangement as claimed in claim 1 wherein a pivot point of the paddle wheel is located below the ink election port.
 4. An ink ejection nozzle arrangement as claimed in claim 1 wherein the side walls include a plurality of circumferential walls located substantially on a circumference of the paddle wheel.
 5. An ink ejection nozzle arrangement as claimed in claim 1 wherein the arrangement includes at least one thermal actuator to control rotation of the paddle wheel.
 6. An ink ejection nozzle arrangement as claimed in claim 5 wherein the, or each, thermal actuator comprises an internal electrically resistive element and an external jacket around the resistive element, the jacket having a high coefficient of thermal expansion relative to the resistive element.
 7. An ink ejection nozzle arrangement as claimed in claim 6 wherein the resistive element is of a substantially serpentine form.
 8. An ink ejection nozzle arrangement as claimed in claim 5 wherein the external jacket comprises substantially polytetrafluoroethylene.
 9. An ink ejection nozzle arrangement as claimed in claim 5 wherein the or each, thermal actuator undergoes circumferential expansion relative to the paddle wheel.
 10. A method of ejecting ink from an ink jet nozzle arrangement having an ink ejection port the nozzle arrangement comprising a plurality of side walls which define a plurality of vane chambers, a pivotally mounted paddle wheel, a plurality of radial paddle wheel vanes attached to the paddle wheel, the paddle wheel vanes being positioned with respect to the side walls and being configured so that rotary movement of the paddle wheel results in each wheel vane rotating with respect to the side walls so that ink within said paddle chambers can be pressurized, said pressurization causing ink to be elected from the ink ejection port, the method comprising the step of rotating each wheel vane with respect to the side walls so that ink is ejected from the ink ejection port. 